To avoid the influence of spontaneous polarization, thermally stimulated current (TSC) measurements of BaTiO 3 -based multilayer ceramic capacitors with Ni internal electrodes were performed within the paraelectric phase. We observed two TSC peaks and inferred that one of them was related to the resistance degradation according to the electromigration of oxygen vacancies. Further, we proposed that the two peaks resulted from the relaxation phenomenon of the oxygen vacancies, which migrated under dc electrical field stresses, in the grains and over the grain boundaries.
Well size-controlled copper fine particles (diameter: 100-300 nm) were used as the inner electrode material of multilayered ceramic capacitors (MLCCs). The particles were dispersed in terpineol to form a printing paste with 50 wt% copper particles. The MLCC precursor modules prepared by the layer-by-layer printing of copper and BaTiO(3) particles were cosintered. Detailed observation of the particles, paste, and MLCCs before and after sintering was carried out by electron microscopy. The sintering temperature of Cu-MLCC was as low as 960 °C. The permittivity of these MLCCs was successfully measured with the copper inner layers.
Electrical properties of defect structure in Ni-doped (Ba1-x
Srx)TiO3 ceramics were studied by means of electron spin resonance (ESR), thermally stimulated current (TSC), dielectric and conduction measurements. A set of experimental results revealed that the nickel cations were located on the B-site of the perovskite in the form of Ni2+ and mainly Ni3+ leading to a slight increase of the diffusion characteristics of the para-ferroelectric transition and that the enhanced electric conduction observed at high temperatures is due to oxygen vacancy migration towards the cathode.
The influence of internal electrode materials on electrical properties in multilayer ceramic capacitors (MLCCs) fabricated by low-temperature co-firing was discussed. The lifetime of MLCCs is considerably improved by using copper rather than nickel internal electrodes. The leakage current density for various dc electric fields (I–V characteristics) and thermally stimulated current (TSC) were measured to investigate the lifetime improvement mechanism. The I–V characteristics demonstrated that the leakage current in a high dc electric field was suppressed in the case of copper internal electrodes. The TSC spectra demonstrated that the internal electrode materials hardly influenced the quantity of polarization charge formed by the electromigration of oxygen vacancies. Therefore, we considered that the improved lifetime by using copper internal electrodes was mainly due to the suppressed leakage current in a high dc electric field, not the quantity of polarization charge formed by the electromigration of oxygen vacancies in the MLCCs.
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